We used a 5110 to calculate contributions from churches to the Diocese of London in 1978 to pay the clergy and central costs. This was a complicated income tax based system at a time of mega inflation. We also ran a property maintenance and expenditure tracking system for 600 houses – data we had never had before. The central church had a couple if 5120s it used to collate the statistics from all 15,000 parishes in England. These replaced magtape on an ICL mainframe. The BASIC was limited by modern standards, but was pretty close to what both the DEC System 10 and the CDC 6600 – both million dollar multi user systems had a few years before. I have just scanned and ported some code that I ran on it to the Vintage Basic compiler running C64 / MS basic and apart from a few tiny changes due to keyboards it runs perfectly. What the 5110 did was it enabled to financial model our diocesan income from churches in an hour. It was a manual 3 day skilled task on 40 column analysis paper. I don’t recollect the disk system being as crude as Joseph (Atlanta states) there was in bult database management with Key index lookup and duplication protection on write. The seek rate was pretty slow by modern standards, it could do about 500 an hour. It seemed quite sophisticated for the time. In 1984 we replaced it with a Fortune 32:16 M6800 system running Unix V7 programmed in C with early Informix RDBMS (still alive today) and 8 terminals. A different world.

Worked on 5110s and 5120s in the NYC commercial printing industry. Wrote an entire job costing system, estimating syste, union payroll system, GL, AP, Billing and AR systems. This was in the 1980s. Had it running at many of the premier large print shops that were all over lower NYC in that period. One configuration had attached "toaster" 8 inch drives. The entire company ran by time slicing their departments. They went on for years until I wrote a conversion program and put them up on a 36 (in Basic). 64K was a thrill to run a full, multi-union, in-house payroll for 50 or so employees across 3 shifts.

I programmed a complete Property-Tax accounting system on one of these IBM 5120 computers, back in 1982... for City Hall in the town where I was living. The 5120 had 32K, no hard drive, just two 8-inch floppy disks, for programs and data. So: no real operating system either. It booted from ROM, and gave you a prompt in APL or BASIC.

As I recall, the style of BASIC was very limited/simplistic. For instance: no "FOR" looping, just use conditional branching. The "IF" statement only had syntax: "IF ABC $ X THEN 2500" where 2500 was a line number to GOTO when the IF-conditional was true. Even the 5120 Disk access was crude. IBM re-used old tape drivers, so the floppy disks would only understand FIXED length FILES, pre-allocated when created... so you needed to plan the Max size for a file in advance, and if that filled up, "too bad" you can''t extend file length... gotta re-build allocations, and copy to another 8" floppy.

However, despite computer''s limitations, I designed and coded a solid Tax accounting system that tracked property owner/address/value/zone for the whole town, calculated taxes, printed mailer statements, collected taxes, logged fees/fines, and allocated funds to appropriate city funds $ levees... which was running for as long as they kept the computer.

The IBM PC was brand new at the time, with more memory and a hard drive, and would have been a better choice$ but managers had already purchased the 5120, and stuck with it.
I guess one of the things I learned from that project is that the right skill for coding/design/efficiency/usability can make more difference than the computer it''s running on... and THAT remains true for system many years later.